Image processing apparatus and correspondence adjustment method

Abstract

This enables the output device to achieve its maximum black density while maintaining continuous gradation in dark areas. [Solution] The image processing apparatus includes a storage unit that stores a correspondence between input coordinate values ​​in an input color space that depends on an input device and output coordinate values ​​in an output color space that depends on an output device, and a processing unit that converts the input coordinate values ​​to the output coordinate values ​​according to the correspondence. The processing unit identifies the darkest point output coordinate value, which is the output coordinate value of the darkest point in the output color space, performs a first adjustment on the correspondence to associate the darkest point output coordinate value with the darkest point input coordinate value, which is the input coordinate value of the darkest point in the input color space, and performs a second adjustment on the correspondence to smooth the output coordinate values ​​corresponding to adjustment points in the adjustment range around the darkest point in the input color space based on the darkest point output coordinate value.

Description

Technical Field

[0001] The present invention relates to an image processing apparatus and a correspondence adjustment method.

Background Art

[0002] In order to represent the color characteristics of a device, a profile such as an ICC (International Color Consortium) profile is used. The profile includes a source profile representing the correspondence between the device-dependent color and the device-independent color in the input color space, a destination profile representing the correspondence between the device-dependent color and the device-independent color in the output color space, and the like. For example, by combining a source profile representing the color characteristics of a display device and a destination profile representing the color characteristics of a printing device, the coordinate values in the output color space for producing the same color as that of the display device on the printing device are determined. The device-dependent color is represented by the coordinate values in a device-dependent color space. The device-independent color is represented by, for example, the color values in a device-independent color space such as the CIE (International Commission on Illumination) L * a * b * color space or the color values in the CIE XYZ color space. Hereinafter, the descriptions of L * , a * , and b * from " * " are omitted.

[0003] Patent Document 1 shows a device link profile that combines a source profile and a destination profile.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] For example, if the darkest point in the input color space is outside the color gamut of the output color space, the darkest point in the input color space will be mapped within the color gamut of the output color space. However, the destination of the mapping in the output color space will not be the darkest point in the output color space. Even if black point correction is performed during mapping, the destination of the mapping in the output color space will not be the darkest point in the output color space. [Means for solving the problem]

[0006] The image processing apparatus of the present invention is A storage unit that stores the correspondence between input coordinate values ​​in the input color space, which depends on the input device, and output coordinate values ​​in the output color space, which depends on the output device. The system includes a processing unit that converts the input coordinate values ​​to the output coordinate values ​​according to the aforementioned correspondence relationship, The aforementioned processing unit, The darkest point output coordinate value is identified, which is the output coordinate value of the darkest point in the output color space, and a first adjustment is performed on the correspondence relationship to associate the darkest point output coordinate value with the darkest point input coordinate value, which is the input coordinate value of the darkest input darkest point in the input color space. The present invention includes a configuration in which a second adjustment is performed on the correspondence relationship, in which the output coordinate values ​​corresponding to adjustment points in the adjustment range around the input darkest point in the input color space are smoothed based on the darkest point output coordinate values.

[0007] Furthermore, the correspondence adjustment method of the present invention is a correspondence adjustment method for adjusting the correspondence for converting input coordinate values ​​in an input color space dependent on an input device to output coordinate values ​​in an output color space dependent on an output device, A first adjustment step involves identifying the darkest point output coordinate value, which is the output coordinate value of the darkest point in the output color space, and performing a first adjustment on the correspondence relationship such that the darkest point output coordinate value is associated with the darkest point input coordinate value, which is the input coordinate value of the darkest input darkest point in the input color space. The embodiment includes a second adjustment step of performing a second adjustment on the correspondence relationship, which smooths the output coordinate values ​​corresponding to adjustment points in the adjustment range around the input darkest point in the input color space based on the darkest point output coordinate values. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic diagram illustrating an example of a printing system configuration. [Figure 2] A block diagram schematically showing an example of a printing system configuration. [Figure 3] A schematic block diagram showing an example of the processing of the profile conversion unit included in an image processing device. [Figure 4] A schematic diagram illustrating an example of profile structure. [Figure 5] A schematic diagram showing examples of the color gamut and darkest point of a device. [Figure 6] A flowchart schematically illustrating an example of print control processing. [Figure 7] A schematic diagram illustrating an example of a user interface screen display. [Figure 8] A schematic diagram illustrating an example of the adjustment range for smoothing output coordinate values. [Figure 9] A schematic diagram illustrating an example of adjusting the device link profile. [Figure 10] A schematic diagram showing examples of input values ​​and output values ​​before and after adjustment. [Figure 11] A schematic diagram showing a modified user interface screen. [Figure 12] A flowchart schematically illustrating a modified version of the print control process. [Modes for carrying out the invention]

[0009] The embodiments of the present invention will be described below. Of course, the following embodiments are merely illustrative of the present invention, and not all of the features shown in the embodiments are necessarily essential to the solution of the invention.

[0010] (1) Summary of embodiments included in the present invention: First, an overview of the embodiments included in the present invention will be described with reference to the examples shown in Figures 1 to 12. Note that the figures in this application are schematic examples, and the magnification in each direction shown in these figures may differ, and the figures may not be consistent. Of course, the elements of this embodiment are not limited to the specific examples indicated by the reference numerals. In "Overview of Embodiments Included in the Present Invention," the text in parentheses indicates supplementary explanation of the preceding word. Furthermore, in this application, the numerical range "Min~Max" means a value greater than or equal to the minimum value Min and less than or equal to the maximum value Max.

[0011] [Aspect 1] An image processing apparatus according to one embodiment (for example, a host device 100) comprises a storage unit U2 and a processing unit U1, as illustrated in Figures 1 and 2. The storage unit U2 stores a correspondence (for example, a device link profile 330) between input coordinate values ​​(for example, RGBin) of an input color space CS1 that depends on an input device (for example, a display device 115) and output coordinate values ​​(for example, CMYKout) of an output color space CS2 that depends on an output device (for example, a printer 2). The processing unit U1 converts the input coordinate values ​​(RGBin) to the output coordinate values ​​(CMYKout) according to the correspondence (330). As illustrated in Figure 6, the processing unit U1 identifies the darkest point output coordinate values ​​(e.g., Co, Mo, Yo, Ko), which are the output coordinate values ​​(CMYKout) of the darkest point (e.g., output darkest point DP2) in the output color space CS2, and performs a first adjustment (e.g., steps S102 to S104, S110) on the correspondence relationship (330) to associate the darkest point output coordinate values ​​(Co, Mo, Yo, Ko) with the darkest point input coordinate values ​​(RGBin) of the darkest input darkest point DP1 in the input color space CS1, which are the input coordinate values ​​(RGBin) of Ro, Go, Bo. Furthermore, the processing unit U1 performs a second adjustment (for example, steps S102 to S104, S112) on the correspondence relationship (330) in which the output coordinate values ​​(CMYKout) corresponding to the adjustment points (for example, grid points GD1) in the adjustment range AR0 around the input darkest point DP1 in the input color space CS1 are smoothed based on the darkest point output coordinate values ​​(Co, Mo, Yo, Ko).

[0012] As described above, the darkest point in the input color space CS1 is converted to the darkest point in the output color space CS2, and the vicinity of the darkest point in the input color space CS1 is smoothed. Therefore, the above embodiment can provide an image processing apparatus that can maintain continuous gradation in dark areas while exhibiting the maximum black density of the output device.

[0013] Various examples can be given to the embodiments described above. Input devices include display devices and printing devices. Input color spaces include RGB color space, CMY color space, CMYK color space, etc. R stands for red, G for green, B for blue, C for cyan, M for magenta, Y for yellow, and K for black. Output devices include printing equipment, display equipment, etc. Output color spaces include CMYK color space, CMY color space, RGB color space, etc. The correspondence between input and output coordinate values ​​can be described using profiles such as device link profiles, calculation formulas, and so on. A profile refers to a set of information that includes one or more lookup tables. In this application, "first," "second," ... are terms used to identify each component included in a group of similar components, and do not imply any order. Of course, the above-mentioned supplementary statement also applies in the following embodiments.

[0014] [Aspect 2] As illustrated in Figure 7, the image processing device may further include a receiving unit U3 that accepts the setting of at least one of the darkest point input coordinate values ​​(Ro, Go, Bo) and the darkest point output coordinate values ​​(Co, Mo, Yo, Ko). In the above case, since the user can arbitrarily set the coordinates of the darkest point, the darkest point can be matched on-site according to the user's preference, thus meeting the diverse needs of users.

[0015] [Aspect 3] As illustrated in Figure 7, the image processing device may further include a receiving unit U3 for receiving the setting of the adjustment range AR0. The processing unit U1 may perform the second adjustment within the set adjustment range AR0. In the above case, the user can set the adjustment range AR0 around the darkest input point DP1, allowing for on-site matching of dark areas according to the user's preference and enabling compatibility with a variety of media with different color characteristics.

[0016] [Aspect 4] As illustrated in Figure 7, the image processing device may further include a receiving unit U3 that receives a setting for smoothing the output coordinate values ​​(CMYKout) corresponding to the adjustment point (GD1). The processing unit U1 may perform the set smoothing process on the output coordinate values ​​(CMYKout) corresponding to the adjustment point (GD1) in the second adjustment. In the above case, the user can determine the smoothing process for the output coordinate values ​​(CMYKout) corresponding to the adjustment point (GD1), allowing for on-site matching of dark areas according to the user's preferences and meeting the diverse needs of users.

[0017] [Aspect 5] The output device may be a printer 2 that forms a printed image IM0 by ejecting an amount of ink 16 corresponding to the output coordinate values ​​(CMYKout) onto a medium 200. The image processing device may further include a receiving unit U3 that receives a setting for the type of medium 200 that forms the printed image IM0 from a plurality of types, including fabric and a second type different from the fabric. When the fabric is set as the type of medium 200 that forms the printed image IM0, the processing unit U1 may perform the first adjustment and the second adjustment on the correspondence relationship (330), and may convert the input coordinate values ​​(RGBin) to the output coordinate values ​​(CMYKout) according to the correspondence relationship (330) after the first adjustment and the second adjustment have been performed. When the second type is set as the type of medium 200 that forms the printed image IM0, the control unit may convert the input coordinate values ​​(RGBin) to the output coordinate values ​​(CMYKout) according to the correspondence relationship (330) in which the first and second adjustments have not been performed.

[0018] Because fabrics are prone to light scattering due to surface irregularities, and ink easily penetrates into the interior, black color reproduction tends to be reduced. In the above embodiment, when the type of medium 200 forming the printed image IM0 is fabric, a color conversion with adjusted dark areas is performed, thus providing a preferable image processing device for printers.

[0019] [Aspect 6] By the way, one correspondence adjustment method is a correspondence adjustment method for adjusting the correspondence (330) for converting input coordinate values ​​(RGBin) of the input color space CS1 which depends on the input device (115) to output coordinate values ​​(CMYKout) of the output color space CS2 which depends on the output device (2), and includes the following steps. (a1) A first adjustment step ST1 is performed on the correspondence relationship (330) to identify the darkest point output coordinate values ​​(Co, Mo, Yo, Ko), which are the output coordinate values ​​(CMYKout) of the darkest point (DP2) in the output color space CS2, and to associate the darkest point output coordinate values ​​(Co, Mo, Yo, Ko) with the darkest point input coordinate values ​​(Ro, Go, Bo), which are the input coordinate values ​​(RGBin) of the darkest input darkest point DP1 in the input color space CS1. (a2) A second adjustment step ST2 is performed on the correspondence relationship (330) to smooth the output coordinate values ​​(CMYKout) corresponding to the adjustment point (GD1) in the adjustment range AR0 around the input darkest point DP1 in the input color space CS1, based on the darkest point output coordinate values ​​(Co,Mo,Yo,Ko).

[0020] The above embodiment can provide a correspondence determination method that can maintain continuous gradation in dark areas while maximizing the black density of the output device.

[0021] Furthermore, the embodiments described above are applicable to an image processing system including the image processing device described above, an image processing method, a correspondence determination program, an image processing program, a computer-readable non-temporary medium on which any of the aforementioned programs are recorded, etc. The image processing device may consist of multiple distributed parts.

[0022] (2) Specific examples of printing systems including image processing equipment and output devices: Figures 1 and 2 schematically illustrate the configuration of a printing system 1, which includes a host device 100 and a printer 2. The host device 100 contains an image processing device. The printer 2 is an example of an output device. The printer 2 shown in Figure 1 is a fabric printer that forms a printed image IM0 on a cloth medium 200, and is a serial inkjet printer. The Y-axis direction in Figure 1 indicates the feed direction D1, which is the direction in which the medium 200 is transported. The X-axis direction in Figure 1 indicates the direction intersecting the Y-axis direction, for example, the width direction perpendicular to the feed direction D1 in the medium 200. The X-axis and Y-axis directions may be horizontal, as shown in Figure 1, or they may be directions other than horizontal. The Z-axis direction in Figure 1 indicates the direction intersecting the X-axis and Y-axis directions, for example, the vertical direction perpendicular to the X-axis and Y-axis directions.

[0023] The medium 200 shown in Figure 1 is a long piece of fabric composed of numerous fibers, with an uneven surface, and supplied in a rolled state. The printer 2 shown in Figures 1 and 2 includes a drive unit 20 to which a head unit 10 is mounted, a print control unit 30 that controls the operation of the printer 2, and the like. Upon receiving print data PD1 from the host device 100, the printer 2 controls the head unit 10 and the drive unit 20 by the print control unit 30 according to the print data PD1, and forms a print image IM0 on the medium 200.

[0024] The head unit 10 shown in Figure 2 comprises an inkjet print head 11 and a head control unit 10c that controls the print head 11. The head unit 10 is mounted on a carriage 41 that can move in a forward direction along the X-axis and in a reverse direction opposite to the forward direction, and moves back and forth with the carriage 41. The drive unit 20 moves the carriage 41 back and forth under the control of the print control unit 30. Under the control of the print control unit 30, the head unit 10 moves in the forward or reverse direction and ejects ink droplets 17 from each nozzle 14 of the nozzle row NL onto the medium 200 that is stopped being transported on the platen 55, thereby forming a dot pattern of ink droplets 17 on the medium 200.

[0025] The print head 11 is capable of ejecting C (cyan) ink, M (magenta) ink, Y (yellow) ink, and K (black) ink as colored inks 16. The print head 11 may also eject inks of colors other than the four colors mentioned above, such as orange or green, or it may eject inks such as processing solutions that fix the colorants of the colored inks, for example, processing solutions that agglomerate the pigments.

[0026] The print head 11 has a nozzle row NL in which a plurality of nozzles 14 are arranged in a nozzle arrangement direction intersecting the X-axis direction, and includes a drive circuit 12, a drive element 13, etc. The plurality of nozzles 14 included in the nozzle row NL may be arranged in a staggered pattern. Each nozzle 14 is capable of ejecting colored ink as ink droplets 17. The drive circuit 12 applies a voltage signal to the drive element 13 according to a drive signal input from the print control unit 30. The drive element 13 can be a piezoelectric element that applies pressure to the ink 16 in a pressure chamber communicating with the nozzle 14, a drive element that generates bubbles in the pressure chamber by heat to eject droplets such as ink droplets 17 from the nozzle 14, etc. Ink 16 is supplied to the pressure chamber of the print head 11 by an ink supply unit 19 such as an ink tank or ink cartridge. The ink 16 in the pressure chamber is ejected by the drive element 13 from the nozzle 14 toward the medium 200 as droplets such as ink droplets 17, and droplet dots are formed on the medium 200. A printed image IM0 consisting of multiple dots is formed on the medium 200.

[0027] The drive unit 20 includes a main scanning unit 40, a transport unit 50, etc., and moves the head unit 10 and the media 200 relative to each other under the control of the print control unit 30. In this specific example, the main scanning unit 40 includes a carriage 41, a guide shaft 42, a carriage motor (not shown), etc., and moves the print head 11 back and forth along the X-axis under the control of the print control unit 30. In this specific example, the transport unit 50 includes a media supply unit 51, a media storage unit 52, a plurality of transport rollers 53, a platen 55, etc., and moves the media 200 in the feed direction D1 under the control of the print control unit 30. The supply unit 51 rotatably supports a reel on which the media 200 is wound in a roll shape and feeds the media 200 to the transport path. The storage unit 52 rotatably supports a reel that winds up the media 200 and winds up the media 200 after printing is completed from the transport path. The multiple transport rollers 53 include drive rollers that move the medium 200 in the feeding direction D1, driven rollers that rotate in conjunction with the movement of the medium 200, and so on. The medium 200 supplied from the supply unit 51 to the transport path is wound into the storage unit 52 via the printing area on the platen 55. Furthermore, when printer 2 performs lateral printing, the carriage 41 equipped with the print head 11 may move in the feed direction D1 and the opposite sub-scanning direction.

[0028] The print control unit 30 includes a communication interface 31, a processor (Central Processing Unit) 32, memory 33, a drive control unit 34, etc., and controls the operation of the printer 2. The communication interface 31 is connected to the communication interface 117 of the host device 100. The communication interfaces 31 and 117 perform bidirectional data communication. The memory 33 includes, for example, semiconductor memory such as ROM (Read Only Memory), semiconductor memory such as RAM (Random Access Memory), and NVM (Non-Volatile Memory). Examples of NVM include non-volatile semiconductor memory such as flash memory and magnetic storage devices such as hard disks. The CPU 32 controls the head unit 10 and the drive unit 20 via the drive control unit 34 by executing a program stored in the memory 33. Furthermore, the print control unit 30 may be configured using an SoC (System on a Chip) or may include an ASIC (Application Specific Integrated Circuit).

[0029] The drive control unit 34 includes a movement control signal generation circuit 35, an ejection control signal generation circuit 36, and a drive signal generation circuit 37, and controls the operation of the head unit 10 and the drive unit 20 based on the control of the CPU 32. The movement control signal generation circuit 35 generates a movement control signal to control the main scanning unit 40 and the transport unit 50 according to instructions from the CPU 32, and outputs this signal to the drive unit 20. The ejection control signal generation circuit 36 ​​generates a head control signal to select the nozzle to eject ink 16, select the amount to eject, control the ejection timing, etc., according to instructions from the CPU 32, and outputs this signal to the head control unit 10c of the head unit 10. The drive signal generation circuit 37 generates a drive signal to drive the drive elements 13 of the print head 11, and outputs this signal to the drive circuit 12. The drive control unit 34 drives the drive elements 13 corresponding to each nozzle 14 based on the head control signal and the drive signal.

[0030] Based on the above, the print control unit 30 controls the main scan, which ejects ink droplets 17 to the print head 11 while moving the carriage 41, and the sub-scan, which feeds a predetermined amount of the medium 200 in the feed direction D1 between main scans.

[0031] The host device 100 shown in Figures 1 and 2 includes a CPU 111, ROM 112, RAM 113, storage device 114, display device 115, operation input device 116, communication I / F 117, etc. These elements 111 to 117, etc., are electrically connected and can input and output information to each other. In this specific example, the host device 100 including the CPU 111 is an example of a processing unit U1, the storage device 114 is an example of a storage unit U2, the display device 115 is an example of an input device, and the host device 100 including the operation input device 116 is an example of a reception unit U3. The storage unit U2 may be RAM 113, an external recording medium RD, or a combination of two or more of storage device 114, RAM 113, and recording medium RD. The host device 100 includes computers such as personal computers (including tablet terminals), mobile phones such as smartphones, etc. The host device 100 may include elements 111 to 117, etc., in a single enclosure, but it may also be composed of multiple devices that are separated and can communicate with each other. Furthermore, the host device 100 and the printer 2 may be located within a common enclosure.

[0032] The storage device 114 stores the operating system, various driver programs including the print control program PR0, application programs, the profile 305 exemplified in Figures 3 and 4, setting information, etc. The print control program PR0 enables the host device 100 to implement functions corresponding to the profile conversion unit 300 and the print data generation unit 400 exemplified in Figure 3. The CPU 111 reads the information stored in the storage device 114 into the RAM 113 as appropriate and performs various processing by executing the read program. The storage device 114 can be a non-volatile semiconductor memory, a magnetic storage device, etc. The computer-readable medium storing the print control program PR0 is not limited to the storage device inside the host device 100, but may also be an external recording medium RD of the host device 100. The display device 115 is a human interface for displaying information, and can be a liquid crystal display panel, etc. The operation input device 116 is a human interface for inputting information, and can be a pointing device, a hard key including a keyboard, a touch panel attached to the surface of the display panel, etc.

[0033] Figure 3 schematically shows an example of processing by the profile conversion unit 300 included in the image processing device. Figure 4 schematically illustrates the structure of profile 305. Profile 305 is a collective term for the input profile 310, also called the source profile, the output profile 320, also called the destination profile, and the DLP (device link profile) 330. The profile conversion unit 300 can also be called a color management system and is implemented in the host device 100 by, for example, a RIP (Raster Image Processor). The profile conversion unit 300 converts input coordinate values ​​in the color space dependent on the input device to output coordinate values ​​in the color space dependent on the output device, according to a profile 305 such as an ICC profile. Here, the input device is a display device 115, the output device is a printer 2, the input color space CS1 is the RGB color space, and the output color space CS2 is the CMYK color space. Figure 3 shows that the components of the input coordinate value RGBin in the RGB color space are (Rin, Gin, Bin), and the components of the output coordinate value CMYKout in the CMYK color space are (Cout, Mout, Mout, Kout). The profile conversion unit 300 generates an output image having output coordinate values ​​CMYKout for each pixel based on an input image having input coordinate values ​​RGBin for each pixel.

[0034] The profile conversion unit 300 can convert input coordinate values ​​RGBin to Lab values ​​by referring to the A2B table 311 included in the input profile 310, and can convert Lab values ​​to output coordinate values ​​CMYKout by referring to the B2A table 321 included in the output profile 320. Lab values ​​refer to coordinate values ​​in the CIE Lab color space. The profile conversion unit 300 can also generate a DLP 330 based on the input profile 310 and the output profile 320, and can convert input coordinate values ​​RGBin to output coordinate values ​​CMYKout by referring to the device link table 331 included in the DLP 330.

[0035] When the profile conversion unit 300 generates an output image from the input image, the print data generation unit 400 generates print data PD1 for forming the print image IM0 based on the output image, and transmits the print data PD1 to the printer 2. For example, the print data generation unit 400 converts each output coordinate value CMYKout of the output image into a gradation value corresponding to the ink usage amount, and generates the print data PD1 by adding a print command to the obtained ink amount data. In this case, when the printer 2 receives the print data PD1, the CPU 32 mainly generates dot data representing the dot formation state based on the ink amount data, controls the drive control unit 34 based on the print command and the dot data, and operates the head unit 10 including the print head 11 and the drive unit 20 in accordance with the print data PD1. That is, the printer 2 forms the print image IM0 by discharging the ink 16 with the ink amount corresponding to the output coordinate value CMYKout onto the medium 200. As described above, the print image IM0 corresponding to the output image from the profile conversion unit 300 is formed on the medium 200.

[0036] As shown in FIG. 4, the A2B table 311 of the input profile 310 is data representing the correspondence between the coordinate values (R i , G i , B i ) in the input color space CS1 that depends on the input device and the coordinate values (L i , a i , b i ) in the profile connection space CS3 which is the Lab color space. The variable i here is a variable for identifying the grid point GD1 set in the input color space CS1. Hereinafter, the coordinate values in the profile connection space CS3 are also referred to as PCS values. When the input color space CS1 is a three-dimensional RGB color space, the grid points GD1 of the A2B table 311 are usually arranged at substantially equal intervals in the R-axis direction, G-axis direction, and B-axis direction in the RGB color space. The A2B table 311 converts the input coordinate values (R i , G i , B i ) into PCS values (L i , a i , b iIt can also be described as a three-dimensional table for converting to RGB values. Although not shown in the diagram, input profile 310 also has a B2A table for converting PCS values ​​to RGB values.

[0037] The B2A table 321 of output profile 320 contains the coordinate values ​​(L) of the profile connection space CS3. j ,a j ,b j ) and the coordinate values ​​of the output color space CS2, which depend on the output device (C j M j ,Y j ,K j This data represents the correspondence between ) and . Here, the variable j is a variable that identifies the grid point GD2 set in the profile connection space CS3. The grid points GD2 in B2A table 321 are usually arranged in the Lab color space at approximately equal intervals in the L-axis, a-axis, and b-axis directions. B2A table 321 is the PCS value (L j ,a j ,b j ) output coordinate values ​​(C j M j ,Y j ,K j It can also be described as a 3D table for converting to ). Although not shown in the diagram, output profile 320 also has an A2B table for converting CMYK values ​​to PCS values.

[0038] The DLP330 is generated by combining the input profile 310 and the output profile 320 according to the rendering intent. The device link table 331 of the DLP330 contains the coordinate values ​​(R) of the input color space CS1. i ,G i ,B i ) and the coordinate values ​​of the output color space CS2 (C i M i ,Y i ,K i This data represents the correspondence between the input coordinate values ​​(R). The device link table 331 contains the input coordinate values ​​(R i ,G i ,B i ) output coordinate values ​​(C i M i ,Yi ,K i It can be said that this is a three-dimensional table for conversion. When the DLP330 is stored in the storage device 114, the storage unit U2 stores the correspondence between the input coordinate values ​​RGBin of the input color space CS1 and the output coordinate values ​​CMYKout of the output color space CS2. In this specific example, the profile conversion unit 300 can be said to be a processing unit U1 that converts the input coordinate values ​​RGBin to the output coordinate values ​​CMYKout according to the DLP330.

[0039] Furthermore, the transformation tables included in profiles (310, 320, 330) are not limited to a single transformation table; they may also be combinations of multiple transformation tables, such as a combination of a one-dimensional transformation table and a three- or four-dimensional transformation table and a one-dimensional transformation table. Therefore, the transformation tables shown in Figure 4 may directly represent the three- or four-dimensional transformation tables included in profiles (310, 320, 330), or they may represent a combination of multiple transformation tables included in profiles (310, 320, 330). Furthermore, a grid point refers to a virtual point placed in the input color space, and it is assumed that the output coordinate value corresponding to the position of the grid point in the color space is stored in that grid point. Multiple grid points may be evenly distributed within the color space, or they may be unevenly distributed within the color space.

[0040] Figure 5 schematically illustrates the color gamut (GM1, GM2) and darkest point (DP1, DP2) of the device. Generally, the color gamut GM2 of an output device differs from the color gamut GM1 of an input device, and the darkest output point DP2 in the output color space CS2 differs from the darkest input point DP1 in the input color space CS1. Figure 5 shows that in dark areas, the color gamut GM2 of the output device is narrower than the color gamut GM1 of the input device, and the darkest input point DP1 is outside the color gamut GM2 of the output device. In this case, the profile conversion unit 300 maps the darkest input point DP1 to the color gamut GM2 of the output device according to the input profile 310, the output profile 320, and the rendering intent. However, the target point NP2 does not become the darkest output point DP2. Even if black spot correction is performed during mapping, the target point NP2 does not become the darkest output point DP2. When DLP 330 is generated from the input profile 310 and the output profile 320 in this state, the darkest input point DP1 is converted to a brighter point NP2 instead of the darkest output point DP2.

[0041] The reason why the mapping target point NP2 does not become the output darkest point DP2 is thought to be because, as shown within the dashed-dot box at the bottom of Figure 5, the output coordinate value of point NP2 corresponding to the input darkest point DP1 is interpolated during mapping according to the B2A table 321 of the output profile 320. In fact, depending on how the output profile 320 is created, the output coordinate value of the output darkest point DP2 may not even exist in the B2A table 321. As mentioned above, the grid points GD2 in the B2A table 321 are discretely arranged in the L-axis, a-axis, and b-axis directions in the Lab color space as the profile connection space CS3. If the Lab value corresponding to the input darkest point DP1 in the A2B table 311 of the input profile 310 does not match any of the grid points GD2 in the B2A table 321, interpolation is performed on the output coordinate values ​​corresponding to multiple grid points GD2. In this case, the mapping target point NP2 of the input darkest point DP1 does not become the output darkest point DP2. Even if black spot correction is performed during mapping, if the target point NP2 does not match any of the grid points GD2 in Table B2A 321, the target point NP2 will not become the output darkest point DP2. For example, in order to interpolate the output coordinate value of point NP2 corresponding to the input darkest point DP1, a grid point GD2 with a CMYK value of (100%,100%,100%,100%) for the output darkest point DP2 is referenced, but as shown in Figure 5, if a grid point GD2 with a CMYK value of (90%,90%,90%,90%) is referenced, the output coordinate value of point NP2 will not become the CMYK value of (100%,100%,100%,100%). In this case, the output coordinate value of point NP2 will have C, M, Y, and K values ​​that are all greater than 90% and less than 100%.

[0042] Furthermore, even if the color gamut GM2 of the output device is wider than the color gamut GM1 of the input device in dark areas, the output coordinate value of point NP2 corresponding to the input darkest point DP1 is interpolated according to the B2A table 321 during mapping, so that point NP2 does not become the output darkest point DP2.

[0043] Therefore, in this specific example, as illustrated in Figure 6 and later, a first adjustment is performed on the DLP330 to associate the darkest point input coordinate values ​​(Ro, Go, Bo), which are the input coordinate values ​​RGBin of the darkest point DP1, with the darkest point output coordinate values ​​(Co, Mo, Yo, Ko), which are the output coordinate values ​​CMYKout of the darkest point DP2. However, the first adjustment alone may result in tonal degradation of the output image, such as crushing of the tonal range of the output image. Therefore, in this specific example, a second adjustment is performed on the DLP330 to smooth the output coordinate values ​​CMYKout, which correspond to the grid point GD1 in the adjustment range AR0 around the darkest point DP1 in the input color space CS1, based on the darkest point output coordinate values ​​(Co, Mo, Yo, Ko).

[0044] (3) Specific examples of processing in a printing system including an image processing device: Figure 6 schematically illustrates the print control process performed by the host device 100, which includes an image processing device. Figure 7 schematically illustrates the UI (user interface screen) 500 displayed on the display device 115 in step S102. Figure 8 schematically illustrates the adjustment range AR0 for smoothing the output coordinate value CMYKout. When the host device 100 receives an instruction to print an image corresponding to the input image onto the medium 200, it starts the print control process shown in Figure 6. Here, steps S102 to S104 and S110 correspond to the first adjustment process ST1, and steps S102 to S104 and S112 correspond to the second adjustment process ST2. The profile conversion unit 300 shown in Figure 3 performs the processing in steps S102 to S116, and the print data generation unit 400 shown in Figure 3 performs the processing in step S118. Hereafter, the term "step" may be omitted, and the step number may be indicated in parentheses.

[0045] When the print control process starts, the host device 100 displays the UI screen 500 shown in Figure 7 on the display device 115 (S102). The UI screen 500 includes an input profile selection field 501, an output profile selection field 502, a rendering intent selection field 503, a darkest point retention checkbox 504, a darkest point input coordinate value input field 505, a darkest point output coordinate value input field 506, a smoothing process selection field 507, an adjustment range selection field 508, an OK button 509, etc. The UI screen 500 displays a "correction function" as the smoothing process and a "correction range" as the adjustment range AR0.

[0046] The host device 100 accepts the selection of an input profile 310 from the profiles stored in the storage device 114 by receiving an operation on the input profile selection field 501 via the operation input device 116. The host device 100 accepts the selection of an output profile 320 from the profiles stored in the storage device 114 by receiving an operation on the output profile selection field 502 via the operation input device 116. The host device 100 accepts the selection of a rendering intent to apply from among multiple rendering intents by receiving an operation on the rendering intent selection field 503 via the operation input device 116. Multiple rendering intents include, for example, "Perceptual," "Media-Relative Colorimetric," "Absolute Colorimetric," and "Saturation."

[0047] The host device 100 accepts the selection of whether or not to retain the scotoma by receiving an operation on the scotoma retention checkbox 504 via the operation input device 116. If the scotoma retention checkbox 504 is checked, the setting is to retain the scotoma; if the scotoma retention checkbox 504 is not checked, the setting is not to retain the scotoma. In addition, if the scotoma retention checkbox 504 is not checked, the host device 100 may not accept operations on the following fields (505 to 508).

[0048] The host device 100 displays the default scotoma input coordinate values ​​(Ro, Go, Bo) in the scotoma input coordinate value input field 505 and accepts operations on the scotoma input coordinate value input field 505 via the operation input device 116. Figure 7 shows that the default scotoma input coordinate values ​​(Ro, Go, Bo) = (0%, 0%, 0%) are displayed in the scotoma input coordinate value input field 505. The user can change the scotoma input coordinate values ​​(Ro, Go, Bo) in the scotoma input coordinate value input field 505 using the operation input device 116. The host device 100 also displays the default scotoma output coordinate values ​​(Co, Mo, Yo, Ko) in the scotoma output coordinate value input field 506 and accepts operations on the scotoma output coordinate value input field 506 via the operation input device 116. Figure 7 shows that the default scotoma output coordinate values ​​(Co,Mo,Yo,Ko) = (100%,100%,100%,100%) are displayed in the scotoma output coordinate value input field 506. The user can change the scotoma output coordinate values ​​(Co,Mo,Yo,Ko) in the scotoma output coordinate value input field 506 using the operation input device 116. For example, if the amount of ink that can be ejected per unit area of ​​the medium 200 is limited, the scotoma output coordinate values ​​(Co,Mo,Yo,Ko) may be changed to (50%,50%,50%,100%) or (0%,0%,0%,100%). Thus, this specific example is also effective for media with a small amount of ink that can be ejected per unit area.

[0049] The host device 100 accepts the selection of a smoothing process from among several smoothing processes by receiving an operation to the smoothing process selection field 507 via the operation input device 116. The multiple smoothing processes include, for example, "linear" which corrects in a straight line, "sigmoid" which corrects in an S-shaped curve, and "spline function" which corrects using spline interpolation. In this example, since the user can change the smoothing process, it can handle a variety of media with different color characteristics.

[0050] The host device 100 accepts the selection of an adjustment range from among several adjustment ranges by receiving an operation on the adjustment range selection field 508 via the operation input device 116. The multiple adjustment ranges include, for example, "wide," "medium," and "narrow." In this example, the user can change the adjustment range, making it possible to accommodate various media with different color characteristics. Figure 8 schematically shows the input color space CS1 as a two-dimensional plane with the R axis and G axis. The actual input color space CS1 is a three-dimensional space with the R axis, G axis, and B axis. The adjustment range AR0 shown in Figure 8 includes the adjustment range AR1 corresponding to "narrow," the adjustment range AR2 corresponding to "medium," and the adjustment range AR3 corresponding to "wide." All of the adjustment ranges AR1, AR2, and AR3 are adjacent to the input darkest point DP1. The adjustment range AR1 shown in Figure 8 is around the input darkest point DP1 in the input color space CS1 and is within a range of one grid point interval from the input darkest point DP1. In this case, the number of grid points GD1 included in the "narrow" adjustment range AR1 is 2 3 -1 = 7. The adjustment range AR2 shown in Figure 8 is the range around the input darkest point DP1 in the input color space CS1, and is two grid points apart from the input darkest point DP1. In this case, the number of grid points GD1 included in the "medium" adjustment range AR2 is 3 3 -1 = 26. The "medium" adjustment range AR2 includes the "narrow" adjustment range AR1. The adjustment range AR3 shown in Figure 8 is the range around the input darkest point DP1 in the input color space CS1, with a grid point interval of 3 from the input darkest point DP1. In this case, the number of grid points GD1 included in the "wide" adjustment range AR3 is 4 3-1 = 63 points. The adjustment range AR3 for "wide" includes the adjustment range AR2 for "medium". The grid point GD1 included in the adjustment range AR1 corresponds to an adjustment point. Furthermore, the adjustment range AR0 can be changed as needed. For example, the "wide" adjustment range AR3 may be a range of 6 grid points apart, the "medium" adjustment range AR2 may be a range of 4 grid points apart, and the "narrow" adjustment range AR1 may be a range of 2 grid points apart. Also, the "medium" adjustment range AR2 is not required for adjustment range AR0, and there may be only two types of adjustment ranges: "wide" and "narrow".

[0051] When the host device 100 receives an operation to the OK button 509 via the operation input device 116, it performs processing according to the display of each area (501 to 508) (S104 in Figure 6). The host device 100 sets the input profile 310 to be used according to the display in the input profile selection field 501 and sets the output profile 320 to be used according to the display in the output profile selection field 502. The host device 100 sets the rendering intent to be applied according to the display in the rendering intent selection field 503. If the darkest point retention checkbox 504 is checked, the host device 100 sets darkest point retention to be executed, and if the darkest point retention checkbox 504 is not checked, it sets darkest point retention to not be executed. The host device 100 obtains the darkest point input coordinate values ​​(Ro, Go, Bo) corresponding to the display in the darkest point input coordinate value input field 505 and obtains the darkest point output coordinate values ​​(Co, Mo, Yo, Ko) corresponding to the display in the darkest point output coordinate value input field 506. The host device 100, including the operation input device 116, can be said to correspond to a reception unit U3 that accepts the setting of the darkest point input coordinate value and the darkest point output coordinate value. The host device 100 sets the smoothing process to be applied according to the display in the smoothing process selection field 507. The host device 100, including the operation input device 116, can be said to correspond to a reception unit U3 that accepts the setting of the smoothing process for the output coordinate value CMYKout corresponding to the grid point GD1. The host device 100 sets the adjustment range to be applied according to the display in the adjustment range selection field 508. The host device 100, including the operation input device 116, can be said to correspond to a reception unit U3 that accepts the setting of the adjustment range AR0. The process of obtaining the scotoma output coordinate values ​​(Co, Mo, Yo, Ko) in S102-S104 can be described as the process of identifying the scotoma output coordinate values.

[0052] After processing in S104, the host device 100 generates an unadjusted DLP 330 based on the input profile 310 and output profile 320 according to the rendering intent (S106). The DLP 330 can be generated, for example, as follows: First, the host device 100 calculates the PCS value (L) of each grid point GD1 in the A2B table 311 of the input profile 310. i ,a i ,b i ) is converted according to the B2A table 321 of output profile 320. At this time, the PCS value (L i ,a i ,b i ) is changed according to the rendering intent. The input value of B2A table 321 is the PCS value L i ,a i ,b i If not, the output coordinate values ​​(C) of multiple grid points in the B2A table 321 that are neighbors to the input value will be generated. j M j ,Y j ,K j Interpolation calculations are performed using ) to obtain the output coordinate values ​​(C) of the device link table 331. i M i ,Y i ,K i The host device 100 then determines the input coordinate value (R) for each grid point GD1. i ,G i ,B i ) and output coordinate values ​​(C i M i ,Y i ,K i A device link table 331 is generated by associating it with the device link table 331. The host device 100 can generate the DLP 330 by storing the generated device link table 331 in the DLP 330.

[0053] As mentioned above, the mapping point NP2 of the input darkest point DP1 does not become the output darkest point DP2 due to interpolation. Therefore, in S106, it is indicated as "DLP before adjustment".

[0054] After generating the DLP330 before adjustment, the host device 100 branches the process depending on whether or not to perform scotoma retention (S108). If the scotoma retention checkbox 504 shown in Figure 7 is checked, the host device 100 performs the scotoma retention process from S110 to S114. If the scotoma retention checkbox 504 shown in Figure 7 is not checked, the host device 100 proceeds to S116 without performing the scotoma retention process. The following describes the darkest spot retention process from S110 to S114.

[0055] First, the host device 100 overwrites the output coordinate values ​​corresponding to the scotoma input coordinate values ​​(Ro, Go, Bo) in the device link table 331 with the acquired scotoma output coordinate values ​​(Co, Mo, Yo, Ko) (S110). Through the processing in S102 to S104 and the scotoma mapping process in S110, a first adjustment process ST1 is performed on the DLP 330 to perform a first adjustment that maps the scotoma input coordinate values ​​(Ro, Go, Bo) to the scotoma output coordinate values ​​(Co, Mo, Yo, Ko).

[0056] After processing in S110, the host device 100 smooths the output coordinate value CMYKout corresponding to the grid point GD1 in the adjustment range AR0 set in the device link table 331 using a smoothing process set based on the darkest point output coordinate value (Co, Mo, Yo, Ko) (S112). Following the processing in S102 to S104 and the smoothing process in S112, a second adjustment step ST2 is performed on the DLP 330, in which a second adjustment is made by smoothing the output coordinate value corresponding to the grid point GD1 in the set adjustment range AR0 based on the darkest point output coordinate value.

[0057] Figure 9 schematically illustrates the adjustment of the DLP330 during processing S110-S112. For clarity, in Figure 9, the input color space CS1 is schematically shown on the horizontal axis as a one-dimensional R axis, with the grid point GD1 shown on this R axis, and the output color space CS2 is schematically shown on the vertical axis as a one-dimensional C axis. In other words, the horizontal axis represents the input coordinate values ​​of R, and the vertical axis represents the output coordinate values ​​of C. The actual input color space CS1 is a three-dimensional space with R, G, and B axes, and the actual output color space CS2 is a four-dimensional space with C, M, Y, and K axes. In Figure 9, the square marks indicate the output coordinate values ​​of C corresponding to the grid point GD1 before adjustment, and the black circles indicate the output coordinate values ​​of C corresponding to the grid point GD1 after adjustment.

[0058] Assume that in the processing of S102 to S104 and the scotoma mapping process of S110, a first adjustment step ST1 is performed by adding an adjustment amount ΔC0 (ΔC0>0) to the output coordinate value of C associated with the input scotoma DP1. In the processing of S102 to S104 and the smoothing process of S112, a second adjustment step ST2 is performed by adding adjustment amounts ΔC1, ΔC2, and ΔC3 according to the set smoothing process to the output coordinate value of C associated with the grid point GD1 in the adjustment range AR0. Figure 9 shows that the adjustment amount of the output coordinate value of the grid point GD11 adjacent to the input scotoma DP1 is ΔC1, the adjustment amount of the output coordinate value of the grid point GD12 adjacent to the grid point GD11 is ΔC2, and the adjustment amount of the output coordinate value of the grid point GD13 adjacent to the grid point GD12 is ΔC3. In the smoothing process, ΔC0>ΔC1>ΔC2>ΔC3>0 is usually the case. When the adjustment amount changes linearly, the output coordinate values ​​are adjusted as follows: for example, ΔC1=(3 / 4)ΔC0, ΔC2=(2 / 4)ΔC0, and ΔC3=(1 / 4)ΔC0. Although not shown in the diagram, the output coordinate values ​​of M, Y, and K are adjusted in a similar manner. As described above, the output coordinate values ​​CMYKout corresponding to the grid point GD1 in the adjustment range AR0 are smoothed based on the darkest point output coordinate values ​​(Co,Mo,Yo,Ko).

[0059] After processing in S112, the host device 100 stores the device link table 331 with the output coordinate value CMYKout adjusted in the DLP 330 (S114). The DLP330 is then adjusted.

[0060] In S116, the host device 100 transforms the input image, which has input coordinate values ​​RGBin for each pixel, according to the device link table 331 in which the darkest spot retention process has been performed, or the device link table 331 in which the darkest spot retention process has not been performed. This generates an output image in which the output coordinate values ​​CMYKout for each pixel. Finally, the host device 100 generates print data PD1 for forming the print image IM0 based on the output image, sends the print data PD1 to the printer 2 (S118), and terminates the print control process. Upon receiving the print data PD1, the printer 2 forms the print image IM0 on the medium 200 according to the print data PD1.

[0061] Figure 10 schematically shows examples of input values ​​and output values ​​before and after adjustment. It is assumed that the input coordinates for the scotomacinous point (Ro, Go, Bo) are (0%, 0%, 0%), and the output coordinates for the scotomacinous point (Co, Mo, Yo, Ko) are (100%, 100%, 100%, 100%). In Figure 10, the input image IM1 is a gradient image in which the components (Rin, Gin, Bin) of the RGB color space coordinate value RGBin change from 0% to 100% while maintaining Rin=Gin=Bin. The converted image IM2 is a CMYK image obtained by converting the input image IM1 according to the DLP330 before adjustment. In the converted image IM2, the output coordinate value CMYKout=(Cout, Mout, Mout, Kout) of point NP2 corresponding to the input darkest point DP1 is Cout<100%, Mout<100%, Mout<100%, and Kout<100%. From this, it can be concluded that point NP2 corresponding to the input darkest point DP1 is not the darkest point.

[0062] The converted image IM3 is a CMYK image in which the first adjustment process ST1 was performed, in which the output coordinate value of point NP2 corresponding to the input darkest point DP1 was replaced with the darkest point output coordinate value (Co,Mo,Yo,Ko), but the second adjustment process ST2 was not performed. In the converted image IM3, the input darkest point DP1 is associated with the darkest point output coordinate value (Co,Mo,Yo,Ko) = (100%,100%,100%,100%). However, in the converted image IM3, the gradation changes abruptly near the darkest point, and the continuity of gradation in the dark areas is not maintained.

[0063] The output image IM4 is a CMYK image in which, in addition to the first adjustment step ST1, a second adjustment step ST2 has been performed to smooth the output coordinate value CMYKout corresponding to the grid point GD1 in the adjustment range AR0 near the input darkest point DP1, based on the darkest point output coordinate value (Co,Mo,Yo,Ko). In the output image IM4, the input darkest point DP1 is associated with the darkest point output coordinate value (Co,Mo,Yo,Ko) = (100%,100%,100%,100%), and the continuity of the dark areas is maintained.

[0064] As explained above, the darkest point retention process shown in Figure 6, S110-S114, is performed, converting the input darkest point DP1 to the output darkest point DP2, and smoothing the vicinity of the input darkest point DP1 in the input color space CS1. Therefore, the image processing device included in the printing system 1 and the correspondence adjustment method performed during the darkest point retention process enable the output device to achieve maximum black density while maintaining continuous gradation in dark areas. This effect can be obtained by changing the module corresponding to the profile conversion unit 300, and can therefore be implemented regardless of the printer model. In this case, the fabric used as the medium 200 is prone to diffuse reflection of light due to the unevenness of the surface fibers, and ink easily penetrates between the fibers, i.e., into the interior, which can easily lead to a decrease in black color reproduction. Therefore, the image processing apparatus and correspondence adjustment method described above are particularly useful for maintaining continuous gradation in dark areas while achieving the maximum black density of the fabric printer.

[0065] Furthermore, if the UI screen 500 shown in Figure 7 does not have input fields 505 for the darkest point input coordinate value and input fields 506 for the darkest point output coordinate value, it will be difficult for the user to understand which coordinate values ​​in the device link table 331 to adjust. By providing input fields 505 for the darkest point input coordinate value and input fields 506 for the darkest point output coordinate value on the UI screen 500, the user can easily associate the input darkest point DP1 with the output darkest point DP2. Since the user can easily perform adjustments to maintain the darkest point, the image processing method and correspondence adjustment method described above are user-friendly.

[0066] (4) Variations: The present invention can be modified in various ways. For example, printer 2 may be a line-type inkjet printer equipped with a print head having a row of nozzles spanning the entire width of the medium 200. The entity performing the above-described processing is not limited to the CPU; it may also be an electronic component other than the CPU, such as an ASIC (Application Specific Integrated Circuit). Of course, multiple CPUs may cooperate to perform the above-described processing, or a CPU and another electronic component (such as an ASIC) may cooperate to perform the above-described processing. The processes described above can be modified as needed, such as by changing the order of operations. For example, in the print control process shown in Figure 6, since the S104 process, which involves obtaining the darkest point output coordinate values, is performed, it is possible to swap the S110 darkest point mapping process with the S112 smoothing process.

[0067] In the UI screen 500 shown in Figure 7, the host device 100 may not accept operations on the input field 505 for the scotoma input coordinate values ​​and may set the scotoma input coordinate values ​​(Ro, Go, Bo) to default values. In this case, the host device 100 accepts operations on the input field 506 for the scotoma output coordinate values, thereby realizing a reception unit U3 that accepts the setting of the scotoma output coordinate values ​​(Co, Mo, Yo, Ko). Furthermore, the host device 100 may set the scotoma output coordinate values ​​(Co, Mo, Yo, Ko) as the CMYK values ​​that result in the smallest L value, for example, based on the A2B table of the output profile 320. Furthermore, in the UI screen 500 shown in Figure 7, the host device 100 may not accept operations on the scotoma output coordinate value input field 506 and may set the scotoma output coordinate values ​​(Co, Mo, Yo, Ko) to default values. In this case, the host device 100 accepts operations on the scotoma input coordinate value input field 505, thereby realizing a reception unit U3 that accepts the setting of the scotoma input coordinate values ​​(Ro, Go, Bo). In addition, the host device 100 may set the scotoma input coordinate values ​​(Ro, Go, Bo) as the RGB values ​​that result in the smallest L value, for example, based on the A2B table 311 of the input profile 310.

[0068] The medium 200 is not limited to being long in length, but may also be cut. Furthermore, the medium 200 is not limited to cloth, but may also be paper such as plain paper, glossy paper, or embossed paper.

[0069] Figure 11 schematically shows a modified version of the UI screen 500. Figure 12 schematically shows a modified version of the print control process. Here, the printer 2 shown in Figures 1 and 2 is capable of switching the type of medium 200 that forms the print image IM0 from a plurality of types, including a first type of fabric and a second type different from the fabric. The UI screen 500 shown in Figure 11 differs from the UI screen 500 shown in Figure 7 in that the darkest spot retention checkbox 504 has been replaced with a media type selection field 520. The elements shown in Figure 11 (501-503, 505-509) are the same as the elements shown in Figure 7 (501-503, 505-509), so a detailed explanation is omitted. The print control process shown in Figure 12 differs from the print control shown in Figure 6 in that the decision process in S108 has been replaced with the decision process in S202. The processes in S102-S106 and S110-S118 shown in Figure 12 are the same as the processes in S102-S106 and S110-S118 shown in Figure 6, so a detailed explanation is omitted.

[0070] When the print control process shown in Figure 12 starts, the host device 100 displays the UI screen 500 shown in Figure 11 on the display device 115 (S102). The host device 100 accepts the selection of the type of media 200 to form the print image IM0 from among the types of available media 200 by receiving an operation to the media type selection field 520 via the operation input device 116. In Figure 11, cloth and plain paper are shown as types of media 200. In this case, plain paper is an example of the second type. Of course, the types of media 200 may include types other than cloth and plain paper, such as glossy paper and embossed paper. When the host device 100 receives an operation to the OK button 509 via the operation input device 116, it performs processing such as setting the type of media 200 to be used according to the display in the media type selection field 520 (S104). The host device 100, including the operation input device 116, can be said to correspond to a reception unit U3 that receives settings for the types of media 200 that form the printed image IM0, including a fabric and a second type different from the fabric.

[0071] After DLP generation in S106, the host device 100 branches the processing according to the type of medium 200 set (S202). If cloth is set as the type of medium 200 that forms the printed image IM0, the host device 100 performs the darkest spot holding processing in S110 to S114. If plain paper is set as the type of medium 200 that forms the printed image IM0, the host device 100 proceeds to S116 without performing the darkest spot holding processing. If the set type of medium 200 is different from cloth and plain paper, that type may be treated as a first type, the same as cloth, or as a second type, the same as plain paper. For example, if embossed paper is included in the first type, the host device 100 performs the darkest spot holding processing in S110 to S114 when a first type such as cloth is set as the type of medium 200 that forms the printed image IM0. If glossy paper is included in the second type, the host device 100 proceeds to S116 without performing the darkest spot holding process when the second type, which includes plain paper and glossy paper, is set as the type of medium 200 for forming the printed image IM0.

[0072] In S116, the host device 100 converts the input image into an output image according to the device link table 331 in which the darkest spot retention process was performed, or the device link table 331 in which the darkest spot retention process was not performed. Based on the above, when cloth is set as the type of medium 200 that forms the printed image IM0, the host device 100 performs the first adjustment and the second adjustment on the DLP 330, and converts the input coordinate value RGBin to the output coordinate value CMYKout according to the DLP 330 that has undergone the first adjustment and the second adjustment. When the second type is set as the type of medium 200 that forms the printed image IM0, the host device 100 converts the input coordinate value RGBin to the output coordinate value CMYKout according to the DLP 330 that has not undergone the first adjustment and the second adjustment.

[0073] Finally, the host device 100 sends the print data PD1 generated based on the output image to the printer 2 (S118). The printer 2 forms the print image IM0 on the medium 200 according to the received print data PD1. As mentioned above, the fabric used as the medium 200 is prone to diffuse reflection of light due to the unevenness of the surface fibers, and ink easily penetrates between the fibers, i.e., into the interior, which can easily lead to a decrease in black color reproduction. The examples shown in Figures 11 and 12 demonstrate that when the type of medium 200 forming the printed image IM0 is fabric, a color conversion is performed that adjusts the dark areas. This is particularly useful for maintaining continuous gradation in dark areas while maximizing the black density of a printer capable of printing on fabric.

[0074] (5) Conclusion: As described above, according to the present invention, various embodiments can provide configurations that enable the output device to exhibit maximum black density while maintaining continuous gradation in dark areas. Of course, even embodiments consisting only of the constituent elements of the independent claims can obtain the basic functions and effects described above. Furthermore, configurations obtained by substituting or changing the combinations of each configuration disclosed in the above-mentioned examples, configurations obtained by substituting or changing the combinations of each configuration disclosed in the prior art and the above-mentioned examples, etc., are also possible. The present invention also includes these configurations, etc. [Explanation of Symbols]

[0075] 1…Printing system, 2…Printer, 10…Head unit, 11…Print head, 14…Nozzle, 16…Ink, 17…Ink droplet, 20…Drive unit, 30…Print control unit, 40…Main scanning unit, 50…Transport unit, 100…Host device, 114…Storage device, 115…Display device, 116…Operation input device, 200…Media, 300…Profile conversion unit, 305…Profile, 310…Input profile, 311…A2B table, 320…Output profile, 321…B2A table, 330…Device link profile, 331…Device link Table, 400...Print data generation unit, 500...UI screen, AR0, AR1, AR2, AR3...Adjustment range, CS1...Input color space, CS2...Output color space, CS3...Profile connection space, DP1...Input darkest point, DP2...Output darkest point, GD1, GD2...Grid points, GM1, GM2...Color reproduction range, IM0...Print image, IM1...Input image, IM2, IM3...Converted image, IM4...Output image, NP2...Point, PD1...Print data, PR0...Print control program, ST1...First adjustment process, ST2...Second adjustment process, U1...Processing unit, U2...Storage unit, U3...Reception unit.

Claims

1. A storage unit that stores the correspondence between input coordinate values ​​in the input color space, which depends on the input device, and output coordinate values ​​in the output color space, which depends on the output device. The system includes a processing unit that converts the input coordinate values ​​to the output coordinate values ​​according to the aforementioned correspondence relationship, The aforementioned processing unit, The darkest point output coordinate value is identified, which is the output coordinate value of the darkest point in the output color space, and a first adjustment is performed on the correspondence relationship to associate the darkest point output coordinate value with the darkest point input coordinate value, which is the input coordinate value of the darkest input darkest point in the input color space. An image processing apparatus that performs a second adjustment on the correspondence relationship, in which the output coordinate values ​​corresponding to adjustment points in the adjustment range around the darkest input point in the input color space are smoothed based on the darkest output coordinate values.

2. The image processing apparatus according to claim 1, further comprising a receiving unit that accepts the setting of at least one of the darkest point input coordinate values ​​and the darkest point output coordinate values.

3. The system further includes a reception unit that accepts the setting of the aforementioned adjustment range, The image processing apparatus according to claim 1, wherein the processing unit performs the second adjustment within the set adjustment range.

4. The system further includes a receiving unit that accepts settings for smoothing the output coordinate values ​​corresponding to the adjustment points, The image processing apparatus according to claim 1, wherein the processing unit performs the set smoothing process on the output coordinate values ​​corresponding to the adjustment points in the second adjustment.

5. The output device is a printer that forms a printed image by ejecting an amount of ink corresponding to the output coordinate values ​​onto a medium. The system further includes a receiving unit that receives the setting of the type of medium from which the printed image is formed, which includes a fabric and a second type different from the fabric. The aforementioned processing unit, When the fabric is set as the type of medium for forming the printed image, the first adjustment and the second adjustment are performed on the correspondence, and the input coordinate values ​​are converted to the output coordinate values ​​according to the correspondence after the first adjustment and the second adjustment have been performed. The image processing apparatus according to claim 1, wherein, when the second type is set as the type of medium for forming the printed image, the input coordinate values ​​are converted to the output coordinate values ​​according to the correspondence relationship in which the first adjustment and the second adjustment have not been performed.

6. A correspondence adjustment method for adjusting the correspondence between input coordinate values ​​in an input color space that depends on an input device and output coordinate values ​​in an output color space that depends on an output device, A first adjustment step involves identifying the darkest point output coordinate value, which is the output coordinate value of the darkest point in the output color space, and performing a first adjustment on the correspondence relationship such that the darkest point output coordinate value is associated with the darkest point input coordinate value, which is the input coordinate value of the darkest input darkest point in the input color space. A correspondence adjustment method comprising: a second adjustment step of performing a second adjustment on the correspondence relationship, which smooths the output coordinate values ​​corresponding to adjustment points in the adjustment range around the input darkest point in the input color space based on the darkest point output coordinate values.

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